From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Test report on the deterioration of nickel ballast resistance wire under various conditions.
| Identifier | ExFiles\Box 54\5\ Scan272 | |
| Date | 6th June 1924 | |
| EFC. {E. Fowler Clarke - Electrical Engineer} 6.6.24. WA. {Mr Wallis} 42. TEST OF BALLAST RESISTANCE WIRE. X.3485. Four tests were carried out with wire from four ballasts, the tests being for the object of ascertaining whether the nickel wire deteriorated at all due to chassis conditions or a prolonged heating test. The results are tabulated as follows :- No.1. 32" Ballast from Lab. This ballast was first subjected to a heating test, being left overnight across a 16 volt battery (fully charged). On examination after this test it was found that the component parts, viz. porcelain and ferrules, etc. were in quite a satisfactory condition. The wire was then removed and drawn out for the purpose of making a tensile load test, the breaking load being 8 lbs. No.2. 15" Ballast off 3-GII. The wire in this ballast when removed and drawn out broke into several pieces and was very brittle, making the load test practically impossible. It was noticed that the other parts of the ballast were quite O.K. No.3. Ballast off 7-GII. This ballast appeared quite O.K. the breaking load of the wire when removed being 8 lbs. 0 ozs. No.4. 25" Ballast from production. This ballast was first given a heating test, being heated to redness for 8 hours across a 16 volt battery. It was observed that the volt ampere characteristic of the wire did not vary appreciably during the whole time. After this test the wire was removed and tested for tensile breaking strength as before. The breaking load being found to be only 5 lbs. 14 ozs. The wire appeared brittle and broke about 2" from the end when being drawn out. A test was then made with a sample of new nickel wire used in making ballasts, and it was found that the tensile load necessary to cause a fracture of the wire was 8 lbs. 14 ozs. From the above it will be seen that the wire does deteriorate slightly under the conditions described above, in the case of the heating test probably due to oxidation, but under ordinary chassis conditions it is not thought this would occur. Of course under extraordinary conditions, i.e. a fully charged battery and short circuited coil primary this might happen. EFC {E. Fowler Clarke - Electrical Engineer} /HEW. | ||